As used in this specification, the term "transparent soap" refers to a one-quarter inch soap section through which a person having 20/20 vision can read 14 point boldface type. This term is not restricted to those soaps which are clear or colorless because it is often desirable to add color to transparent soap. The present invention contemplates both colored and clear transparent soaps.
For commercial acceptance, transparent soaps must retain all the quality characteristics of conventional, opaque soap (such as good lather, hardness, mildness, minimum sluffing and the like). These products must remain transparent under normal use for extended periods of time. U.S. Pat. Nos. 3,793,214 and 3,926,828 describe known, but inferior, formulations made by neutralizing a mixture of saturated fatty acids and aliphatic monocarboxylic acid with a pH adjusting agent containing alkanolamines.
The present invention includes, inter alia, the production of transparent soaps comprised of sodium tallowate, sodium cocoate and non-volatile polyhydric alcohols, in which the pH is adjusted with citric acid. Transparent products made from the presently disclosed soap formulations have all of the desired qualities of conventional, opaque soap and additional features which permit economic and safe production.
Currently known soap formulations do not retain transparency when remelted, making it impractical to economically recycle excess waste. Conventional techniques also require aging, a process which evaporates volatile, short-chain monohydric alcohols. This aging process is time-consuming, expensive and potentially hazardous to production personnel.
The ability of soap to be remelted and retain all of its original qualities is critical for reducing costs. During production, a large reserve of scrap soap accumulates. This scrap is frequently discarded because it cannot be remelted to form a product which exhibits the original features. Lages U.S. Pat. No. 3,969,259; Verite U.S. Pat. No. 4,980,078 and Lindberg U.S. Pat. No. 4,468,338 disclose state-of-the-art transparent soap preparations which are subject to these deficiencies. These and other references demonstrate the need for a remeltable formulation to dramatically reduce production costs.
The traditional method for making transparent soap involves forming a solution of ingredients in a volatile solvent (commonly ethanol), casting the pourable mixture into large mold frames and allowing the volatile solvent to evaporate. Solidified soap is semi-opaque when initially cast. Solvent evaporation creates the transparent qualities of each formulation. But, evaporation is time-consuming and commonly causes a weight loss in excess of 15 percent.
For example, soap bars produced according to Chambers U.S. Pat. No. 4,988,453 must initially contain 6 to 15 percent volatile, low molecular weight alcohols (such as methylated spirits, ethanol and isopropanol) which require an aging period of several days to achieve transparency. In addition, the aging-evaporation procedure releases alcohol vapors which require expensive measures to reduce the hazards of exposure.
Other problems are known to the art. Typical casting methods cause shrink deformation resulting from the evaporation of alcohol and moisture. Transparent bars frequently have inferior end-use properties, despite higher retail prices when compared to opaque counterparts. Known transparent soaps frequently develop a sticky, opaque surface layer when placed in contact with water. And, high alkaline content can cause skin dryness. Soap bars which typically display these problems are produced according to the disclosures of Fromont U.S. Pat. No. 2,820,768; Poper U.S. Pat. No. 4,290,904 and Jungermann U.S. Pat. No. 4,758,370. They are sold commercially under the trade name "Neutrogena."
The present disclosure provides, inter alia, formulations which include sodium soap and polyhydric alcohols in critical weight percent ranges. These ingredients are mixed with specific acids to adjust the pH condition. Disclosed formulations produce soap products that do not require aging to obtain transparency, can be remelted and have the ability to accept color. This invention also provides a mild formulation which exhibits all the qualities of a conventional, high quality soap.
It is an object of the present invention to provide formulations and methods for making transparent soaps which do not require lengthy aging procedures or the use of hazardous, volatile, low molecular weight alcohols to achieve transparency.
Another object is to provide a transparent soap which can be remelted to achieve acceptable transparency using recycled production scrap.
A further object is to provide formulations for making transparent soaps which do not form undesirable opaque sluff-residues during or after end use application.
Yet another object is to provide transparent soap bars with exceptional gloss-like clarity and enhanced stability to light, heat and oxygen.
Still another object is to provide transparent soaps having excellent odor profiles with or without incorporation of a fragrance.